Cancer is the second leading cause of death among children, but despite extensive research, the etiology of childhood cancers remains largely unknown. The workplace is an important source of environmental chemicals and other agents and these exposures may be inadvertently transferred to the fetus or to the home. Research on parental occupational exposures and childhood cancer has suggested several links, but there remain areas of research that are understudied, with one of the most notable gaps being a lack of information on maternal occupational exposures. We propose a large (N=537,000) nested case-control study of children born in Denmark 1965-2010 to examine risks of cancer from parental occupational exposures. Cases will be taken from the Denmark Cancer Registry and controls will be selected at random from the Denmark Central Population Registry. We will have additional information on each child's peri-natal history from the Medical Births Registry. Information on parental job titles is available from the Central Population Registry and information on industry of employment will be taken from the Supplementary Pension Fund, a supplement to the state pension that was established in 1964 and retains information on all employed persons residing in Denmark. We will further use job-exposure matrices that have been previously developed for studies of occupational health in Denmark. Our aims are to focus on maternal occupational exposures and specific hypotheses of suspected carcinogens that have been observed in the literature. This proposal presents an exciting opportunity to identify specific cancer-occupational links, with the possibility of informing policy on workplace safety regulation and encouraging research on therapeutic and preventive strategies.